Paraffin alkylation process promoted with silica gel and aluminum bromide



W 1961 G. R. GILBERT ETAL 2,978,524

PARAF'FIN ALKYLATION PROCESS PROMOTED WITH SILICA GEL AND ALUMINUMBROMIDE Filed Dec. 1, 1958 2 82 or- 042 Z 0:0: 0 mac .1; N N S 1 N m :125 3 o N m N F! I 5 r 5% N O O 10 m E %w :12 m i (59 2 mg do o um: 3 mmH: 5 um: 42 34: 9 J r mo 0: IE 0 a :1:

George R. Gilbe n Alon Schneshenn Inventors John E. McCormick By Q MAttorney PARAFFIN ALKYLATION PROCESS PROMOTED WITH SILICA GEL ANDALUNHNUM BROMIDE George R. Gilbert, Elizabeth, Alan Schriesheim, Fords,and John E. McCormick, Roselle Park, N.J., assignors to Esso Researchand Engineering Company, a corporation of Delaware Filed Dec. 1, 1958,Ser. No. 777,282

9 Claims. (Cl. 260-68353) This invention relates to a process whereinbutanes and/or pentanes are alkylated with higher paraflin hydrocarbonsto produce branched chain parafiin hydrocarbons boiling in the motorfuel range. In particular the invention concerns a process wherein abutane or a pentane is reacted with a parafiin hydrocarbon of from 6 to18 carbon atoms in the presence of aluminum bromide and a promoter underconditions that favor the production of high yields of branched chainparaffin hydrocarbons of from to 7 carbon atoms.

With the increased use of modern high compression engines in theautomotive industry the petroleum refiners have encountered a majorproblem in supplying a sufficient quantity of motor fuels of high octanerating to satisfy the requirements of those engines. Heretofore thesupply of gasoline components has been augmented by using C and Cpetroleum fractions as starting ma:

Patented Apr. 4, .1961

2 able source. A portion of the stream is conducted via line 11a throughan aluminum bromide pick-up vessel 12 to dissolve aluminum bromide in aportion of the stream that is conducted to the reaction zone. Theremainder of the feed stream is combined with the effluent leaving thepick-up vessel via line 13 and is conducted into a reaction zone 15. Thelatter zone contains one or more beds of silica gel saturated withaluminum bromide.

A stream of a higher paratfin hydrocarbon, as for. ex-

ample heptane, octane, dodecane or cetane, or of mix tures containingthe higher paraflins, is conducted into the reaction zone by means ofline 16. Preferably the stream enters the reaction zone at a pluralityof spaced points, 16a, 16b, etc., so as to insure as high a ratio aspossible of isobutane to higher paraflin at any particular point in thereaction zone. a

The reaction product leaves the reaction zone through line 18 and isconducted into an initial separation zone terials for making higherhydrocarbons principally by if polymerization and alkylation processes.Thus for example isobutane can be reacted with butylene in the presenceof sulfuric acid to give a branched chain 8- carbon-atom alkylate. Alsobutylene can be polymerized to a C unsaturated hydrocarbon which uponhydrogenation will give isooctane. These processes have somedisadvantages in that they require a number of separate operations andin that they necessitate the use of olefins which are usually inrelatively limited supply.

It has now been found that, by the use of a promoted aluminum bromidecatalyst, butanes and/or pentanes can be reacted directly with higherparatfin hydrocarbons to give good yields of C to C branched chainhydrocarbons of high octane rating, provided certain specific conditionsare employed. to conduct reactions'of this type but yields have beenlow, reaction rates have been uneconomic and satisfactory productdistribution has not been obtained.

In accordance with the present invention, a paraffin It has previouslybeen proposed 1 hydrocarbon-of from 6 to 18 carbon atoms is reacted witha large excess of a butane or a pentane, preferably isobutane, employingas a catalyst A1Br supported on or associated with silica gel, attemperatures in the range of schematic flowlplan of one ,process forpracticing. the invention.

The process will be described with'particular reference tothe use ofisobutane as the lighter component. Referring to the drawing in detail,a suitable butane feed stream containing at least initially a majorproportion of isobutane is obtained by means of line 11 from. a-suiti 20wherein light materials including unreacted isobutane and normal butane,are removed overhead and recycled to the reaction zone by means of line21. Hydro,- gen bromide, which is preferably present, will also berecycled via line 21. The heavier material, including C hydrocarbons andhigher, is conducted by means of line 22 into a product separation zone24 wherein C to C hydrocarbons are removed overhead by means of line 25while heavier material comprising C hydrocarbons and higher as well asany aluminum bromide that has been removed from the reaction zone isrecycled to the reaction zone by means of line 26. If desired,conditions can be adjusted in separation zone 24. to include normalheptane in the heavier material recycled through line 26, whileincluding the C branched chain isomers in overhead line 25.

In place of isobutane the feed in line 11 may comprise normal butane, inwhich case no higher hydrocarbon feed stock will be sent initially tothe reaction zone but 7 able cracking occurs and the principalproducts'are pro- 7 pane and lighter materials. Also it has beenestablished that aluminum bromide alone or even in'the presence ofconventional hydrogen halide promoters such as hydrogen bromide, in theabsence of the support, is very.

much less active than the catalyst system of the present invention.Furthermore in order for the reaction to proceed satisfactorily it isnecessary that suflicient alumi 1 if num bromide be present not only tosaturate the support I under the reaction conditions employed but alsoto leave at least a small amount dissolved in the reacting hydrocarbons.

A mixed catalyst in which a portion of the aluminum bromide is replacedwith aluminum chloride may be used provided that at least some aluminumbromideis present in the reacting hydrocarbons over and above that whichis adsorbed on the support.

Although the reaction may proceed in the absence of hydrogen bromidepromoter it is preferred that it be used as an auxiliary promoter inaddition to the silica gel A range of from about 0.1 to 8% or more ofHBr by weight based on total feed may be used, while from about 2% toabout 5% is preferred. The hydrogen bromide is introduced into thereaction zone by means of line. 17 and is recycled to the reaction zonealong with unreacted butanes by means of line 21.

Although the process as described in conjunction with the drawingcontemplates downflow of the stream through the catalyst bed, which ispreferred, upflow can also be used. Also in place of a fixed bedprocess, a moving bed of catalyst could be used. Alternatively, a slurrytype of operation could be employed wherein a suspension of catalyst ismaintained in the reacting hydrocarbons, the slurry being stirred in thereactor with suitable mechanical stirring means or recirculated throughthe reactor by pumping means. Where slurry operation is used, the slurryis removed from the reactor at the end of the reaction period, in thecase oi batch operation, or as a fraction of the circulating stream inthe case of; continuous operation, and sent to suitable separationequipment to separate the catalyst from the hydrocarbons. The separationequipment may comprise a simple settling tank, a centrifuge, or afilter, for example, or suitable combinations of such means.

It is preferred that the minimum mol ratio of isobutane and/orisopentane to higher parainn be about 3 to 1 but should preferably be nohigher than about 12 to 1. If sufficient iso-C is not present in thereaction zone to efiect alkylation of the materials obtained when ahigher parafiin or other higher product of the reaction is cracked bythe catalyst, catalyst sludging will result. The feed stock must beessentially free of aromatic hydrocarbons and not more than about 0.02%of such material should be present. An added advantage of the catalystsof the present invention is that naphthene hydrocarbons may be toleratedin the feed stock up to about 20 volume percent. With increasednaphthene content the reaction severity must be increased somewhat ascompared to a reaction in the absence of naphthenes. This may beaccomplished by raising the temperature and/or lowering the feed rate,for example.

Feed rates may vary from about 0.3 to about 2 v./hr./v. (liquid volumeof total feed per hour per volume of total catalyst plus support) thehigher feed rates being preferred when little or no naph-thenes arepresent.

To remove aromatics from the feed stock conventional techniques may beemployed such as solvent extraction, hydrogenation, acid treating andthe like, as well as treatment with selective absorbents such asmolecular sieve zeolites. It is not necessary that the higherhydrocarbons used be individual hydrocarbons such as heptane or octaneor cetane, for example, but mixtures may be used, such as a petroleumfraction containing paraifinic hydrocarbons in the range of 6 to 18carbon atoms. Although, as stated, hexane is one of the higherhydrocarbons that may be used, it is preferred to employ heptane orhigher. Essentially the same product distribution is obtained withhexane as with heptane but the reaction rate is lower by a factor ofabout 3. Other sources of the higher parafiin hydrocarbons for thereaction include light virgin naphthas, and paraffin raflinates from theextraction of hydroformed petroleum fractions.

At the start of the process the silica gel may be saturated withaluminum bromide and then placed in the reaction zone, or,alternatively, the silica gel alone may be placed in the reaction zoneand then saturated with aluminum bromide carried in with a portion ofthe feed. Another method of preparation is to mix the aluminum halidewith the support and to heat the mixture to effect impregnation. Ifdesired, loosely held aluminum halide may be removed from the catalystmass by heating the mass and passing through it a gas such as carbon dioxide, methane, hydrogen or nitrogen.

Alternatively the support may be impregnated by dissolving the aluminumhalide in a suitable solvent such as ethylene dichloride or dioxane, forexample, and the porous carrier impregnated with this solution, followedby heating to remove the solvent and loosely held aluminum halide. Stillanother alternative is to employ a powdered support or promoter, mix thealuminum halide with it, and compress the mixture into pellets.

The following examples serve to illustrate the practice of the presentinvention.

Example 1 Comparative tests were made in which in each instance amixture of 160 cc. of isobutane and 40 cc. of a normal heptane feed(containing n-C and 5% of methylcyclohexane) was stirred for 3 hours at72 F. with one of the catalyst systems identified in Table I. At the endof each run the yield of products was determined. the results also beingpresented in Table I.

Table 1 Test 1 Test 2 Test 3 Test 4 Catalyst, grams:

AlBr; 23. 6 23. 6 23. G 23. t Silica gel 47. 2 47. 2 HBr 24. 0 .l. 1

Analysis of (Id-Product, Weight percent:

iso-Os 0. 4 0. 5 12.3 31!. 0 n-Cs 0.3 3. 6 1.0 3.7

0. 5 0. 3 14. 9 l) 7 0 0 U. 6 l l 46. 2 48. 3 (i5. 6 38. (l 52. 6 47. 3l l. t

Total C7 Q8. 8 95 6 68. 7 39. .5

C's-l- I. 0 l 2 It will be seen from the results of these comparativetests that aluminum bromide alone, or even in the presence of hydrogenbromide, was not eifective in producing the desired reaction. In both ofthese instances the major proportion of the reaction products comprisedC hydrocarbons. The aluminum bromide merely served as an isomerizationcatalyst. On the other hand, in the tests in which aluminum bromide andsilica gel either alone or in conjunction with hydrogen bromide wereemployed as the catalyst, considerable yields of C and Cs isomers wereobtained. Since the total weight of the reacting hydrocarbons was about118 grams, the 2.4 grams of HBr in Test 4 equalled about 2 weightpercent, based on total feed. It will be seen that the catalyst activitywas greatly enhanced by that amount of hydrogen bromide.

EXAMPLE 2 In a manner similar to that employed in Example 1 comparativetests were made with a number of other supports instead of silica gel.These included pumice, sand, powdered quartz and Fe O The samecatalystto-support ratios were used, as well as the same reactiontemperature and time, and the same hydrocarbon feed as in Example 1.None of the supports other than silica gel was found to be efiective inpromoting the desired reaction. In each case from about 96.5 to about99% of the product comprised C hydrocarbons althrough some isomerizationof the normal heptane had taken place.

E AM L 3 Two forms of silica gel were compared for their activity inpromoting aluminum bromide in the reaction of isobutane and. normalheptane. One of these was a granular silica gel and the other was aspray dried silica gel. The physical properties of these two forms ofsilieage a e com ar d in Tab e .II-

Table I] Table IV Surface Pore Pore RunA RunB Area, Vol. Radius, mJ/g.cc./g. A. r

5 Wt. Percent AlBr in Feed.. 0. 2 0.06 704 21 151 riluolilggrswgurzgfiio-50 50-80 80-100 20-70 145-185 1i eii s? "di iIzoe 63 C5 -1 -1. so a0 636 r1 i2 i8 s3 12 it Using the same hydrocarbon-feed and the samereaction conditions as in Example 1 the two forms of EXAMPLE 5 silicagel were compared using equal weights of silica H gel and aluminumbromide. The results obtained at .Usmg the same P110t eq EX P 4 the endof a 3 hour reaction period are shown in Table l fs a catalystmllfitllfe conslfitmg 0 equal III. It will be seen that the'spray driedsilica gel was Q of gel and alumlnum m i Pulls were a more activepromoter 'for the desired reaction than 15 made In Whlch the amount o YP b o added the granular sill-ca geL to the feed and the amount o fa1um1num bromide added 7 were vaned. Reactron conditions were the sameas in Table III Example 4. -When employing 2 percent hydrogen bromideand 1 percent aluminum bromide it was found that Granular spray thecatalyst activity remained relatively constant; With Silica Dried 2percent aluminum bromide and 2 percent hydrogen Gel ag bromide thecatalyst activity remained relatively constant and at a' somewhat higherlevel than with 1 percatalystz cent aluminum bromide (roughly 20 percentmore AiB grams 47-2 47-2 active). When only 1 percent hydrogen bromidewas f 3352 5 -w y g z g employed along with 2 percent aluminum bromidethe catalyst activity dropped to $4; of its original value in 5969' 2:?i; about 60 hours.

d Other studies have established that in order to obtain the desiredreaction it is necessary to have present in 0 '0 the reaction zonesufficient aluminum bromide so that 08 aluminum bromide will be presentin solution in. the hydrocarbons over and above the quantity required toi504}, 58.9 40.1 satisfy the total adsorption capacity of the silicagel. -01 i To ensure such a condition incontinuous operation it Totalc,6M 4L5 is preferred that sufiicient aluminum bromide be dissolved in atleast one of the entering streams of reacting hydrocarbons so that aminimum of 0.1 weight percent of aluminum bromidebased on feed is sentto'the EXAMPLE 4 40 reaction zone. As brought out in Example 5 it isalso A catalyst composition comprising silica gel and alugig g gi g igggj i g rgf g 55322 5 3X gggg g gig fi ig g g yg g g g g ggg ii gg taincatalyst activity in continuous operation. Preferpilot unit consistingof a jacketed reactor provided with i g 2 to 5 weight percent ofhydrogen bromlde 23 5 2 33 lfgg gg ggg g gifi gif sg 6%: Although in theillustrative examples given, the higher P and 150 p g pressure- A feedmixture of normal para ifin hydrocarbon reactant comprised heptane,other hptane and which gave about 70 volume studies have shown that withhydrocarbons of greater 7 percent of isobutane in the reactor was passedthrough molecular Sue-h as. Octaneicetane or octadecape the reactor at aspace velocity of about 0.05 volume of gg ggg distnbunon ls essentiallythe Same as wlth trier 5:51:32?atzziztezaifla narrate :33: ore Wl occur0 1 r u :rithateagerness? 20232? 242a; g g ously added to the reactionzone as a solution inisobug g p f 1 i L d 5 tane in sufiicient quantityto furnish a 2 wt. percent rocar 15 afger m Proporlon o y focal.-solution based on total feed. Hydrogen bromide was bons than is desired.the Product may be i to added at the rate of 2 wt. percent based on thefeed. i a F whlch P than be used a The total liquid product from thereactor was scrubbed tlonal aliylatlon step with an .olefin such asethylepe with 20% caustic to remove aluminum bromide and propylene or abutfineaempioymg the u sual hydrogen bromide, then dried, debutanizedand analyzed. catalysts as Sulfur: aFId! acid y After 50 hours ofoperation the addition of aluminum gen fiuonde, or an alummumAlternatlvelyw bromide to the feed was discontinued. At the end of the 5can befall 0 8 Second reaction zone of the an additional 50 hours ofoperation the activity f the type herein described for reaction withhigher normal catalyst for the desired reaction was less than 10% of Phydrocarbonsits initial activity as shown in Table It lS tO beunderstood that this invention is not to A Second run was made in thepilot i using a be l mited to the specific embodiments and examplescatalyst composition comprising equal weights of silica herein desfmbedand Presented P that Its scope 15 to gel and aluminum bromide andcontinuously adding alube deteTI n1ned b y the clalms pp heretominumbromide in sufficient quantity to furnish 0.2 wt. What IS clalmedpercent based on total feed for the first 50 hours and A Process for thePreparation of high Octane subsequently to furnish 0.06 wt. percentbased on feed. naphtha components consisting largely of branched chainThe product was treated and analyzed in the same paraffin hydrocarbonsof 5 to 7 carbon atoms which manner as in the first run and the resultsobtained are comprises reacting a minor proportion of a straight chainalso shown in Table IV. paraffin hydrocarbon of from 6 to 18 carbonatoms with a major proportion of a lighter hydrocarbon selected from thegroup consisting of butanes and pentanes, at temperatures no higher thanabout 140 F., in a reaction zone in the presence of a catalystcomprising aluminum bromide and silica gel and maintaining in thereaction zone at least 0.06 weight percent aluminum bromide in solutionin the reacting hydrocarbons in addition to the quantity required tosatisfy the total adsorption capacity of the silica gel.

2. Process as defined by claim 1 wherein from about 0.1 to about 8percent of hydrogen bromide, based on the reacting hydrocarbons, ispresent in the reaction zone.

3. Process as defined by claim 1 wherein the mol, ratio of said lighterhydrocarbon selected from the group consisting of butanes and pentanesto said hydrocarbon of from 6 to 18 carbon atoms in the reaction zone isin the range of from about 3 to 1 to about 12 to l.

4. Process as defined by claim 1 wherein naphthenic hydrocarbons arepresent in said reaction zone.

5. Process as defined by claim 1 wherein the temperature of the reactionis in the range of about 50 to about 120 F.

6. Process as defined by claim 1 wherein said silica gel is in the formof spray dried microspheres.

7. A process for the preparation of high octane naphtha componentsconsisting largely of branched chain paraflin hydrocarbons of from 5 to7 carbon atoms which comprises reacting a minor proportion of a straightchain paraflin hydrocarbon of from 6 to 18 carbon atoms with a majorproportion of a lighter hydrocarbon selected from the class consistingof butanes and pentanes, at temperatures no higher than about 140 F., inthe presence of a catalyst comprising silica gel saturated with aluminumbromide, continuously conducting reacting hydrocarbons into saidreaction zone at a rate such that the mol ratio of said lighterhydrocarbon selected from the group consisting of butanes and pentanesto said hydrocarbon of from 6 to 18. carbon atoms in the reaction zoneis in the range of from about 3 to 1 to about 12 to 1, continuouslyadding to at least one of the entering streams of reacting hydrocarbonsat least 0.1 weight percent of aluminum bromide based on the totalhydrocarbon feed, and continuously removing reaction products from saidreaction zone.

8. Process as defined by claim 7 wherein from 2 to 5 weight percent ofhydrogen bromide, based on total hydrocarbon feed is added to at leastone of said entering streams of reacting hydrocarbons.

9. A process for the preparation of high octanenaphtha componentsconsisting largely of branched chain parafiin hydrocarbons of from 5 to7 carbon atoms which comprises reacting a minor proportion of a straightchain paratfin hydrocarbon of from 6 to 18 carbon atoms with a majorproportion of a lighter hydrocarbon selected from the group consistingof butanes and pentanes, at temperatures no higher than about F., in thepresence of a catalyst comprising silica gel saturated with aluminumbromide, continuously conducting said reacting hydrocarbons into saidreaction zone, continuously adding at least 0.06 weight percent aluminumbromide based on reacting hydrocarbons to said reaction zone, andcontinuously removing reaction products from said reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS2,349,458 Owen et a1. May 23, 1944 2,370,144 Burk Feb. 27, 19452,401,925 Gorin June 11, 1946

1. A PROCESS FOR THE PREPARATION OF HIGH OCTANE NAPHTHA COMPONENTSCONSISTING LARGELY OF BRANCHED CHAIN PARAFFIN HYDROCARBONS OF 5 TO 7CARBON ATOMS WHICH COMPRISES REACTING A MINOR PROPORTION OF A STRAIGHTCHAIN PARAFFIN HYDROCARBON OF FROM 6 TO 18 CARBON ATOMS WITH A MAJORPROPORTION OF A LIGHTER HYDROCARBON SELECTED FROM THE GROUP CONSISTINGOF BUTANES AND PENTANES, AT TEMPERATURES NO HIGHER THAN ABOUT 140*F., INA REACTION ZONE IN THE PRESENCE OF A CATALYST COMPRISING ALUMINUMBROMIDE AND SILICA GEL AND MAINTAINING IN THE REACTION ZONE AT LEAST0.06 WEIGHT PERCENT ALUMINUM BROMIDE IN SOLUTION IN THE REACTINGHYDROCARBONS IN ADDITION TO THE QUANTITY REQUIRED TO SATISFY THE TOTALADSORPTION CAPACITY OF THE SILICA GEL.